SCARCITY OF ICOSAHEDRA IN QUENCHED SIMPLE ATOMIC LIQUIDS

In an extension of an earlier study [F.H. Stillinger and R. A. LaViolette, Phys. Rev. B 34, 5136 (1986)], amorphous deposits were quenched at constant volume from each of two model one-component atomic liquids for a range of densities in which the corresponding crystalline phase is close packed. That study concluded that local icosahedral coordination in monatomic amorphous substances was rare, in conflict with other reports of abundant icosahedral coordination. Here, in an attempt to find circumstances which might favor icosahedral arrangements, one of the liquids was cooled below its vitrification temperature before quenching. In another attempt, both liquids were quenched at various densities, which in some cases produced deposits under tension. Nevertheless, for all cases considered here, fewer than 1 in 1000 twelvefold-coordinated atoms possessed an icosahedral arrangement of its neighbors. These results are combined with those reported elsewhere in order to conclude that local icosahedral arrangements cannot serve as a motif for the disorder in amorphous deposits of simple atomic substances, in contrast to the claims of other studies. © 1990 The American Physical Society.